Transmission dynamometer



Feb.' -16 ,1926.

J. W. LEGG TRANSMISSION DYNAMOMETER Filed Jan. l4, 1921 INVENTOR Josep/2 W Lcyy wlNEsSEs:

, ATTORNEY katented elo. l, i926.

WCE.

ELECTRIC & MANUFACTURING: COMPANY, A CORPRATXON OF PENNSYLVANLL.

/TRNSMSSXN Application led Z'anuary 14;, 19521. I Serial No. 437,171.

To all whom' t may concern.' A

Be it known that L JOSEPH W. lince, a citizen of the United States, and a resident of l/Vilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful improvement in rlransmission Dynamometers, of which the followingl is a specification.

'My invention relates to transmission dym namometers and it has particular relation to vdevices of the character described that are adapted to be employed to determine the torque of rotating machines.

@ne of the objects of my invention is to i5 provide a means for determining the amount Vof the opposition that a machine will exert against any action which tends to accelerate or retard the rotation thereof with respect to a predetermined speed, which opposingI force will be hereinafter termed either positive or negative torque.

Another object of my invention is to provide a dynamometer by means'of which the positive or negati-ve torque of a dynamoelectric machine or other prime mover vbe indicated upon a calibrated dial by means of an electric spark. Y K

Another object of my invention is to pro- 2 vide a device of the class described that may be caused to indicate the' torque of an electric motor from zero to maximum speed lay' means of. a rapid svuppession of electric sparks, one occurring upon eachlrotation of the motor shaft.

A further object of my invention is to provide a dynamometer, the dial lof which may be illuminated at the proper point, to enable the operator to quickly and easily read the amount of the torque of the machine'being tested, as indicated upon the dial. 1

Another object of myinvention is to provide a device of the character designated that shall be adapted to record the torque 5 characteristics of a dynamo-electric machine in permanent form for future examination and' comparison. 1'

In the accompanying drawings, Figure 1 is a side elevational `view of a m dynamometer constructed in accordance withmy invention and'shown as coupled between two dynamo-electric machines, one of which i to be tested. Figui? is a vertical transverse section, tak- Fig. 2 but on a larger scale and illustratinga graduated strip of paper or chart disposed in the path of the sparking elementsl to obtain a permanent record of the torque characteristics of the machine being tested.

Referring to the drawings, a machine, which is illustrated as an electric motor 1, is to be tested to determine the amount of the torque thereof. lThe motor( 1 is provided vvith a shaft 2 and is preferably disposed in axial alinement with the shaft 3 ofa dynamo-electric machine 4 having a larger capacity than the motor 1.

The machine @may be either a motor or a generator but is preferably a direct-current, variable-speed motor, the speed of rotation of which may be adjusted to oppose any change in the speed of the motor 1. The machine 4, therefore, functions as a speed regulator kor governor for the machine 1.

A collar 5 is fixed to the end of the'shaft 3 of the machine i adjacent to the motor 1 and is yieldably connectedl to a similar col lar 6 carried by the shaft 2 of the motor 1, by means of a coiled spring 7, the torsional characteristics of which have been predetermined. lhe collar 6 is mounted for axial movement upon the shaft 2 by means of a spline yor feather key 8 to compensate for any contraction or expansion of the spring during" the operation of the machine.

A disc 9.. of insulating material is mounted upon abase 10 adjacent to the collar 5 p and is provided with a centrally disposed aperture l1n through which extends the ,shaft 3 of the machine 4. The disc 9 is further provided with a scale 11 adjacent to the periphery thereof which may be suitably calibratedlto indicate', in foot pounds, the positive or negative torque of the'motor being tested, when used in connection with flexible means of known torsional character! ptilized for this purpose butva disc, such as that described, is preferably employed by g' reason of the fact that it reduces the friction caused by windage and also shades the eyes of the operator from the glare of the indicating spark.

-The disc 12 is also provided with a spark-L ing electrode 14 adjacent to the pointer .13

and fs adapted to co-operate with an annular electrode 15 thatv is mounted in the face of the stationary insulating disc 9 and is spaced from, and disposed adjacent to the path of, the rotatable electrode 14. An electric spark is established across they gap thus ,formed once every rotation of the shaft 2 v by means of the following circuit.

The current from one terminal of a' battery .1.6 flows through a conductor .17 to a rotating make-and-breakv contact device 18 carried by the shaft 2 of the motor 1 from whence it intermittently flows through the frame of the motor 1, conductor 19, primary winding of an induction coil 20, conductor` 4through a conductor 23 to the electrode 14.

i When the circuit is broken by the contact device 18, the current th'us induced' discharges across the gaptbetween. the electrode 14 and the annular electrode 415 in the form `of a spark and illuminates the face of the dial adjacent to the point thereon designated by the indicator 13. -The current then flows, through the annular electrode '15, bindingpost 24 and a conductor 25, to the coil 20. j Y

Both of the circuits thus outlined may be provided with a common ground connection '26 to prevent an excess of potential from being built up inthe circuit.

If it i's desired to ascertain the amount of i the positive torque of the motor 1, the operation of the'machine is as follows: The motor l is started and the machine 4 is so energized as to have atendency `to rotate at a slower speed than the motor 1. The motor 1 will then accelerate the rotation of the machine 4 which, therefore, will function as a generator and retard the actionof the `motor 1. ThisXbraking action of the ma- 4chine 4, uponthe rotation ofthe shaft 2,

causes the distortion of the spring 7 and so' a consequent lagging of the pointer 13 with respect to its normal position. The result,

l .ing retarding action exerted by lthe variable'- speed machine, 4 in 'opposition to' that of the motorfl may-be regulated Vat th(` will of the operator according tothe'estimated torque,l speed or other characteristics pecutested.

liar to the particular typeof machifnefbeing If, on the other hand, it is desired to ascertain the negative torque of the tor 1, lthe same is Ienergized to rotate at a iertain speed and the lmachine 4 is energized to have a tendency to operate at a greater speed. The machine 4, therefore, will accelerate vthe speed of the motor 1, `and the latter will oppose the rotation of .the,machine` 4 and functions as a generator. The retardation thus exerted by 'the motor 1 upon t-he machine 4 will exert a torsional force upon the spring 7 whichl will effect ay consequent deflection of the pointer 13 in the opposite direction.

It will be apparent that, if the motor 1 and the machine 4 are both so operated as to give the machines the same speed, there will be no torsional force exerted upon the spring 7 and the pointer 13 will remain in its zero position throughout the operation.

From the above description, it will be noted that the machine 4 will'have the effect of a speed regulator orygovernor. and, being of a larger capacity than the motor 1, will tend, at all times,`to cause the motor '1 to operate in synchronism therewith. That is, if the machine 4 is adjusted to operate at a certain speed, the machine 1 may be adjusted to run at a greater or slower speed and the machine 4 will, in either case, oppose the machine 1 and tend to bring the latter into synchronism with the machine 4.

When the switch 22 is in its closed position, a spark will be caused to occur between the electrodes 14 and 15 once every-,rotation of the shaft 2, by the contact device 18. c

The spark thus formed is'in alinement with the position of the pointer 13 with respect to the dial 11 and not only indicates the position of the rapidly rotating pointer 13 at the breaking of contacts 18 but villumina'tes the face of the dial adjacent thereto.

A tachomete'r may be attached to the shaft 2 of the motor 1, and the torque of thc'- motor, as indicatedupon the dial, may .be compared with'the rotations'per minute of the shaft 2 at any particular speed. The switch 22 may be normally-maintained in an open position and be closed when it is desired to determine the torque of the machine at a certain number of revolutions per minute.

In Fig. 8 of the drawing, I- have illustrated means for obtaining a graphic record` `of the torquecharacteristics of a motor at' speeds ranging from zero `to maximum, which may be preserved for future examina.- tion and comparison. A strip of paper 27, or other suitablematerial, is shown as being wound upon a lower spool28 from which it passes-upwardly through a slot 29 and between the disc L12 and the dial 11, 'and is woundlupon a similar spool 30.

the center of the electrode 14. The arcuatelines may be graduated in revolutions per minute, progressing from Zero speed to full speed. As the paper moves, thus bringingl the arcuate lines successively opposite the path of the electrode, the operator adjusts the speed' of the machines 1 an'l t accordingly anc, at each different speed, when the switch 2 is closed, the' spark will puncture the paper in accordance with the change in its displacementI at that speed. rlhus, a rec ord, as shown by the dots on the arcuate lines, will be made of the torque atleach different speed,A the value of which torque is, determined .by the portion of the puncture mark along the line representing the speed at the time the mark was made.

ln the drawing, l/ have shown a roller 31 adapted to frictionally engage the surface of the paper tol feed it lupwardly and the roller is actuated by means of suitable gearing 82 and a shaft 33 actuated by the shaft 3 of the lmotor through the medium of suitable reduction gearing, not shown.

With this arrangement, the paper is moved in proportion to the speed of the ma.-

-chines and the paper 27 may accordingly be marked at its edges to represent time intervals, instead of speeds, as in the above described operation. rllhus, if the switch 22 be closed automatically at equal intervals of time, by any suitable means (not shown), the longitudinal distance between the puncture marks is proportional to speed, and the distanceacross the paper between the puncture marks and the zero position of the pointer is proportional to torque.

By my invention, -a complete record of the torque characteristics of the motor may be graphically obtained, overa range from full speel in one direction to'full speed in the opposite direction, and also the amount of the torque which resists any tendency to accelerate the speed thereof is recorded in permanent form for future study and comparison. lf operated manually, the switch 22 may be normally left open and the paper adjusted with the li'ne representing the desired'revolutions per minute in aposition coinciding with the path of the electrode 14.

As soon as the tachometer reading corresponds to that indicated upon the paper strip, the switch 22 is closed, which causes a spark to jumplbetween ,the electrodes 14 and 15 to perforate the chart'ata position indicating the torque of,the.motor at that particular speed. This operation may be periodically repeated .when themachine attains certain speeds or revolutionspper minute until a complete record of the torque of the motor is indicated graphically upon the chart.

M'y invention is not limited to the specific structures illustrated as it is adapted to be variously modified without departing from the spirit and scope of the invention, as set forthin the appended claims.`

l claim as my invention:

l. ln a dynamometer, the combination with a' plurality of relatively movable members and vieldable connecting means therebetween, of indicating means comprising a circuit including a space-discharge electrode moved in accordance with the movement of one of said members, a stationary co-operating electrode conforming to the path of movement of said movable elect-rode in spaced relation thereto. and means actuated by the other member for controlling the energization of said circuit. 3

ln a dynamometer, the combination with a pair of axially alined rotatable mem-` bers and vieldable connecting means therebetween, of indicating means comprising a circuit including a space-discharge electrode rotated in accordance with the rotation of one of said members,l a stationary electrode having a co-operating circular space-'discharge portion conforming to the path of movement of said movable electrode in spaced relation thereto and a circuit-making-and-breaking device actuated by the other rotatable member.

3. A, dynamometer comprisingC a pair of axially alined shafts, yieldable connecting means therebetween including a collar xed to one of said shafts, a collar longitudinallyslidably keyed to the other shaft and a spring connecting said collars. a space-discharge electrode carried by said fixed collar, a stationary electrode having a portion conforming to the path of movement of said movable electrode in spaced relation thereto. and means on said other shaft for controlling space discharges between said electrodes.

4t. A dynamometer comprising a rotatable device to affect the speed of operation of a `machine to be tested, means for yieldably connecting said device to said machine, a scale member provided with a sparking electrode, an indicatingr member.; for cop-operationwith said scale member and provided with a sparking electrode adapted to co-opcrate with the irst mentioned electrode, one of said"y members being carried bysaid connecting `means and the other being stationary relative thereto, and means f'o/r estabf lishing electric sparks betweenvsaid electrodes lat time intervals determined by the speed of the mrchine.

5. A dynamometer comprising means including a rotatable member adapted to vary the speed of operation of a machine to be tested, means for yieldably connecting said member Vto said machine, a rotatable sparking electrode carried by said connecting means, a stationary scale mounted adjacent to said rotatable' electrode, an Aannular .sparking electrode 'carriedby said scale and disposed adjacent to the path of said rotatable electrode, and means .connected to Said` electrodes across said yeldable con'- necting means andcontrolled in accordance with the operation of the machine for inter- -'mittently establishing an electric spark between said electrodes to indicate upon said scale the amount of the torque exerted by ,said machine upon said braking device.

6. A dynamometer comprising a rotatable member adapted'A to vary the speed of operation of a machine tobe tested, means 4for yieldably'connecting said rotatable member to' said machine', a stationary dial mounted .adjacentto said retarding means, a rotatable indicating member mounted on said retard-` ing member for co-operation with said dial, means connected to said electrodes across l said yieldable -connecting means and controlled'in accordance with the operation of 25 the machine, ada ted to cause an electric spark to occur a jacent to said indicating member, and a chart disposed in the path or said spark.

7 InV a dynamometer, the combination with a pair of axially alined shafts and yieldable connecting means therebetween, of a discoidal member carried by one of said shafts having a pointer element adjacent to its perimeter and carrying a sparking electrode on one surface, a stationary similar member disposed in slightly-spaced parallel relation to said surface having an annular scale outside the perimeter of the other member and an annularco-operating electrode on its inner surface inside said scale,

and means on said other shaft for controlling discharges between said electrodes.- In testimony whereof, I have hereunto subscribed my name this 5th day of J anuary, 1921.

JOSEPH W. LEGG. 

